The role of the lymphatic system in the absorption and distribution of antitumor agents and other substances (serum albumin, tumor cells, latex microspheres and liposomes) administered to rats by ip, iv or sc routes is under investigation. The importance to lymphatic absorption of the molecular weight and lipid solubility of the agents and the vehicle or formation in which they are given is also being evaluated. Studies on lipisomal encapsulation of adriamycin, ara-C and melphalan are in progress. The lymphatic absorption, physiologic disposition, toxicity and antitumor activity of liposome-encapsulated adriamycin administered by ip and iv injection to rats is being evaluated and compared with that of free adriamycin. Efforts are underway to develop a reproducible model system in rodents for tumor metastasis via lymphatic channels, so that the therapeutic advantage of treating such tumors with antitumor agents selectively taken up by lymphatics can be tested. Studies on the mechanism of absorption from the peritoneal cavity, with emphasis on the significance of the lymphatic system, are in progress.